“It was a good battle," Federer told Sky Sports' Annabel Croft during his on court interview. "I always enjoy coming out to a
beautiful arena like The O2 in London. It is a city I have had so much fun
playing in.

“I was trying to put a lot of balls into play so there was a
lot of defending from me tonight but at the end it paid off so I am extremely happy.”

Zverev crunches a forehand winner to move 30-0 ahead on the Federer serve. The world No 2 recovers the deficit only to push a crosscourt forehand into the tramlines. Federer saves the break point when Zverev goes long with a backhand on the run. Zverev saves it with a perfectly executed lob over Federer which lands just inside the baseline. A further game point is saved but Federer eventually secures the hard fought service hold with a couple of heavy forehands which prove too strong for Zverev.

Critical moments in this final set for Zverev. From 40-15 ahead he conspires to lose three points on the spin, including making two successive unforced errors on the forehand side to hand Federer a game point. The Swiss great secures the double break lead when a sliced backhand forces another error. Surely that's Federer firmly in control now!

Federer consolidates the break of serve with a love service hold. Can the world No 2 continue to make the break advantage count just as he failed to do in the second set. Everything is looking rosy for the 19-time Grand Slam champion at the moment.

Zverev follows a seventh double fault of the match with an unreturned first serve down the tee to leave the game at 15-30. Federer punishes a mid court ball on the forehand wing to bring up two game points. Moments later Federer secures the early break in the decider when Zverev hits backhand wide into the tramlines.

Zverev complains over a line call which appeared long to the naked eye but chair umpire Damien Dumusois called it in and a Federer overhead eventually won the point. Zverev can only push a backhand return into the net to allow Federer a comfortable service hold.

Federer produces a couple of uncharacteristic unforced errors to hand Zverev three set points and despite seeing the first two disappear, a wayward forehand hands the break to the German. Huge character from the 20-year-old to turn around that set. We are going the distance!

Out of the six singles matches we have seen this week only one has finished in straight sets. The public inside The O2 are getting their money's worth.

Zverev continues his aggressive baseline tactics to good effect moving within one game of the second set thanks in part to a backhand down the line which is too strong for Federer to handle. Will we be heading for another tiebreak or will Zverev break for the second time in the match to force us into a decider?

Zverev continues to hold his nerve under pressure and moves into the lead once again with a service hold which is epitomised by the German's ability to gain the upper hand off his serve. Federer will serve to stay in this second set. That didn't likely half an hour ago when the world No 2 moved into a 2-0 lead...

Federer lobs up an easy overhead which he swats away with ease to bring up a break point at 30-40 on the Federer serve. The Swiss quickly serves himself out of trouble with an unreturned serve and another netted return hands the world No 2 a game point. A masterful backhand volley by Federer dips over the net for a winner.

The German world No 3 continues to find a high percentage of first serves and thanks to the weight of ball he is managing to find secures a comfortable service as Federer makes a couple of unforced errors.

A double fault by Federer hands Zverev an opportunity of a break at 30-30. A crosscourt forehand into the net enhances the German's chances to regain parity. Somehow the world No 2 escapes from a losing position to guide a backhand winner past the German who was rooted at the net. A sixth ace of the match for Federer saves the second break point. However the 19-time Grand Slam is unable to save a third as the world No 3 fires a forehand winner down the line. Impressive from the German. That's Federer broken for the first time in the match.

A double fault by Zverev hands Federer three break points in the opening game of the second set and despite Zverev saving the first two he is unable to take the game to deuce. The momentum continues to go in Federer's direction.

Federer benefits from a timely net cord to help him to parity at 4-4. A forehand wide into the tramlines hands Zverev his first set point but he is unable to close it out as he fails to time a crosscourt forehand for a winner. The pendulum continues to swing before Zverev's forehand fails him at 6-7 to hand the world No 2 the set. What a climax to a high quality first set. Fifty-five minutes on the clock. That must be hugely deflating for Zverev.

Zverev secures the early minibreak advantage in the tiebreak when a forehand down the line by Federer goes wide. An ace out wide on the deuce court then moves the German into a 3-0 lead. Federer pumps his fist as he walks to the change of ends with a reduced deficit as the 20-year-old is unable to control a backhand.

Gutsy stuff from Zverev. He saves a set point when Federer can only put a backhand into the net. A gruelling baseline exchange follows at deuce which sees Federer perfectly time a half-volley onto the baseline to bring up a second set point. Moments later the German is counting his blessing as he benefits from a net cord. Moments later he brings up game point before forcing us into a tiebreak as Federer frames a backhand long. What a game. Riveting encounter.

At 30-15 Zverev unleashes on a backhand down the line which proves too strong for Federer's racket. Federer responds with a classy forehand winner to move 40-30 ahead. The pair play out a brutal baseline exchange and it is Zverev who loses his patience first coughing a dumped slice into the middle of the net. There's an electric atmosphere inside The O2 and the crowd are enjoying the contest.

Zverev offers up an easy overhead for Federer who takes full advantage to get to 40-30 on the Zverev serve but an ace down the tee from the German keeps up level in the opener. Who will buckle under the pressure first?

The German makes a sneaky move to the net and puts Federer on the back foot and the Swiss is only able to push the backhand into the tramlines. That's successive service holds to love for the 20-year-old. On we go.

Still no breaks in the first set as Federer stays ahead with an authoritative service hold. These games are racing by. The German will serve next with new balls as we head to the crunch stage of the opener.

Zverev goes for a rising forehand drive winner but gets it all wrong and the ball sails beyond the baseline, narrowly missing a line judge to miss out on moving 30-0 up in the game. Moments later Zverev wins a hard-hitting exchange from the baseline to bring up two game points. Federer mixing up the speeds in that exchange before he drifted a slice wide. A backhand loops long to hand Zverev the service hold. Federer noticeably retreating well past the baseline to return the Zverev serve - even on the German's second serve.